Among all reports regarding the latest advances of communication technologies, the Next Generation Network (NGN) and the Third Generation mobile communication (3G) are undoubtedly the two realms attracting the most attention.
The definition of the NGN has varied all the time during its development. In the “Global NGN Summit 2004” sponsored by the International Telecommunication Union (ITU), a standard NGN is defined as a packet based network that can provide various services including telecommunications services and can use transport technologies that may provide a variety of wide bands and a Quality of Service (QoS), thus establishing the ultimate orientation and scope for the advancement of the NGN.
In fact, the NGN is also the foundation for bearing future 3G services, and holds a particularly important place among future telecommunication networks. Therefore, global telecommunication standardization organizations, major telecommunication operators and telecommunication equipment providers each devote huge amounts of labor and money to the improvements of NGN technologies, and various NGN commercial trial offices have been put into use by some global operators, a success of which may accelerate the advancement of the NGN in turn.
In view of the deployment of the current NGN, a Media Gateway Controller (MGC) and a Media Gateway (MG) are substantially the two essential components usually used for networking. Here, the MGC is responsible for the call controlling function and the MG is responsible for the service bearing function, thus enabling the separation of the call-controlling plane from the service-bearing plane. These two planes can evolve independently from each other, and hence share network resources sufficiently, leading to a simplification of device updates and service extensions and also a reduction of development and maintenance costs.
FIG. 1 shows the networking mode of an MG and an MGC in the NGN. As shown, a protocol network 1 is a transport network for all protocols, a media gateway controller 10 interfaces with a media gateway 11 via a media gateway control protocol 110, and the media gateway controller 10 interfaces with a media gateway 12 via a media gateway control protocol 120.
The media gateway 11 and the media gateway 12 are connected via a real-time transport protocol 140 under the control of the media gateway controller 10. An internet protocol 130 bears the transport of the media gateway control protocol 110, the media gateway control protocol 120 and the real-time transport protocol 140 in the protocol network 1. A user terminal 13 has an access to the protocol network 1 through the media gateway 11, and a user terminal 14 has an access to the protocol network 1 through the media gateway 12. An interaction between the user terminal 13 and the user terminal 14 may be enabled via the various devices and the protocols between the various devices in the protocol network 1.
As seen from FIG. 1, in addition to the two essential components of MGC and MG, the media gateway control protocols therebetween plays a significant role in the network. Two media gateway control protocols widely used at present are the H.248/MeGaCo (Gateway Control Protocol) and the MGCP (Media Gateway Control Protocol).
The MGCP is a media gateway control protocol established by the Internet Engineering Task Force (IETF) in 1999, and the abstract model defined by the MGCP includes two main concepts of “Endpoint” and “Connection”.
The Endpoint is a data source or sink, which may be a physical or virtual endpoint. The Endpoint represents an entity providing a certain function on an MG, and as well known to those skilled in the art, such entities may include a Time Division Multiplex (TDM) channel, a digital channel, an analogous line, a recording server access point and an interactive voice response access point.
The Connection represents a call-related resource combination on an MG, for example, an association of a TDM channel with a Real-time Transport Protocol (RTP) stream, and the like. It shall be noted that the Connection may be a uni-connection (e.g. in the case one TDM channel is associated with one RTP stream) or multi-connection (e.g. in the case one TDM channel is associated with a plurality of RTP streams). A continuation of a call is essentially an operation for both an endpoint and a connection based upon such abstract models of the protocol.
An MGC and an MG interact with each other through a Command request and a response. The MGC can request to be informed by the MG upon detection of certain events such as an occurrence of Off Hook, On Hook, Flash Hook or Dialing, etc. or can request a loading of certain signals onto an Endpoint, such as Dialing Tone, Ring-Back Tone, Busy Tone and the like.
The parameters with service dependencies are logically aggregated as a package, and as well known to those skilled in the art, a package includes events and signals and is supported by a specific endpoint. Particularly, each event or signal may be indicated with a “PackageName/EventName” or a “PackageName/SignalName”, each kind of endpoints has a specific package, each package contains regular events and signals, and the package name and the event name or the signal name are both represented by a character string.
The common networking modes and the common communication protocols between the essential components of the NGN have been described as above. It shall be particularly noted that any new technology for a communication network shall offer a support to the original services without exception of the NGN. The metering pulse was ever one of important services in the Public Switched Telephone Network (PSTN), and mainly used for the charging of public telephones. While inheriting the demand of the PSTN services generally, the NGN shall enable the metering pulse service with the coordination of the MGC and the MG. In practical applications, however, the MGCP lacks a signal and a solution for implementing the metering pulse.